In case of machinery being supplied with water via attached hoses, machinery such as a washing machine, and especially in case of such machinery being located inside a home, it is advantageous to detect water escaping from the machinery and/or attached hoses, as quickly as possible, and to then stop the flow of water.
Of the prior art in this area, U.S. Pat. No. 5,190,069 teaches a device for shutting off water to a pipe when sensing water leaking from the pipe, with the sensing provided by a sensor based on a tape including spaced apart conductors and liquid cell sensor elements and wrapped around the pipe. The conductors are insulated from each other everywhere except in the liquid cell sensor elements, where they are stripped bare but still held in spaced-apart relation. When water enters a liquid cell sensor element, it provides a conducting path between the two stripped-bare portions of the two conductors in the cell.
U.S. Pat. No. 4,386,231 and U.S. Pat. No. 4,598,277 each teach using two conductors disposed in spaced apart relation and held so by insulating material, in an arrangement in which leaked water provides a conducting path connecting the two conductors. The '231 patent shows conductors on an insulating substrate/tape, and teaches the optional use of porous material for covering the conductors on the insulating substrate/tape. The '277 patent shows fabric mesh holding conductors in spaced-apart relation, and teaches impressing a voltage across the conductors and arranging that the voltage so impressed gives rise to a warning in case of a leak.
All of the above-mentioned patents disclose devices useful in not only detecting a leak, but also for indicating the location of the leak. To do so—i.e. to not only detect a leak but also to determine its location—a relatively elaborate construction is required. In the latter two patents, a sensor is used of a type that confines the effect of the leak to the location where the leak first occurs. In the first patent, a different sensor is used in each of several different zones. Also in the first patent, the construction of each sensor is complicated by the aim of avoiding sensing water that has merely condensed onto the sensor equipment, as opposed to water actually leaking (i.e. in some significant quantity) from a pipe.
Compared to the rather more industrial-grade sensor devices of the prior art, what is still needed for many applications—especially residential—is a sensor and controller apparatus that is relatively simple and easy to install, and so more reliable and also less expensive.